It's a very dark blue, which is 95% opaque after applying one coat of nail polish. To brighten it up a bit, I used my very own River and the Tardis as a second coat on my ring fingers, with Have an Ice Day from Catrice as a third coat.

Personally, Bleu Nuit is a bit too dark for me, almost black sometimes. But it will be a great base to put effect polishes on top.